Among previous sheet forming machines, there is a sheet forming machine disclosed in, for example, Patent Document 1. The sheet forming machine of the patent document is constituted to obtain a sheet forming body of a predetermined shape through obtaining a wet sheet form by sucking in moisture by suction box 4 provided below sheet forming belt 3 while transporting a raw material slurry made of a mixture of cement, pulp, or the like discharged from discharge opening 2 of raw material supply tank 1 by sheet forming belt 3, and cutting the sheet form with cutter 5, as shown in FIG. 1. Sheet forming belt 3 is usually constituted by felt or the like and mounted in a loop form between breast roll 6, which is provided to locate below discharge opening 2 of raw material supply tank 1, and bottom couch roll 7 which is provided to be spaced by a predetermined distance from the breast roll. Then, sheet forming belt 3 is inclined upward from the near side of a portion below discharge opening 2 toward bottom couch roll 7 side such that the discharged raw material slurry stays in the vicinity of a portion below discharge opening 2 and a sheet form can be made in order from the lower face of the sheet forming body. At inclined portion 8, although it is not shown, side plates are disposed in an upright fashion at both sides of sheet forming belt 3.
In each sheet forming body manufactured by the sheet forming machine, there is a problem that variations in the thickness in the width direction thereof occur due to the state of concentration, fiber length, grain size, or the like of the raw material, pollution of a felt, rapid spread in the width direction of the raw material which is supplied to inclined portion 8, or slowing of the speed of flow of the raw material in the vicinity of side plates of inclined portion 8. Also, since the raw material moves in the width direction of sheet forming belt 3 at inclined portion 8, so that only one raw material can be selected as the raw material of the sheet forming body, there is a problem that it is not possible to obtain a sheet forming body which is integrated in longitudinal stripe shapes by using different raw materials or raw materials of different colors in the width direction of sheet forming belt 3.
Patent Document 1: JP-UM-B-52-31325